Zesty Lime Sugar Bars

Preheat your oven to 350°F.
Line a 15x10-inch baking pan with foil, ensuring that the foil extends over the edges.
Zest the limes to get 4 teaspoons of zest and squeeze 5 tablespoons of juice from them.
In a large mixing bowl, beat together the softened butter and shortening using a mixer on medium to high speed for about 30 seconds.
Add the granulated sugar, baking powder, salt, and 3 teaspoons of the lime zest.
Continue to beat until the mixture becomes light and fluffy, scraping the sides of the bowl as needed.
Incorporate the eggs, vanilla, and 3 tablespoons of lime juice, beating until well combined.
Finally, beat in the all-purpose flour.
Spread the batter evenly in the prepared pan.
Bake for 20 to 25 minutes or until the bars turn light brown.
Allow them to cool slightly in the pan on a wire rack.
To make the glaze, stir together the powdered sugar, the remaining 1 teaspoon of lime zest, and 4 teaspoons of lime juice in a small bowl.
If needed, add more lime juice to reach a thin glazing consistency.
Spread the glaze on the still-warm, uncut bars, and let them cool completely.
Use the foil to lift the uncut bars out of the pan, then cut them into individual bars.